Bone grafts are commonly used to treat defects in the skeletal system caused by injury or disease. Skeletal defects often require bone grafts to maintain space and provide a matrix for healing. A graft should provide or facilitate the various mechanisms of bone healing including osteoconduction, osteoinduction, and osteogenesis.
Osteoconduction is the ability of the graft to act as a matrix or scaffold to support bone formation. Osteoinduction is a result of bone growth factors that stimulate differentiation of local cells to become bone forming cells, i.e. osteoblasts. Bone morphogenic proteins (BMP's) that are naturally occurring in bone, or that may be produced by recombinant gene technologies, are responsible for osteoinduction. Osteogenesis refers to the formation of bone, and may also be used to reference the ability of cells, to form bone. Bone forming cells may either be resident at the graft site or transplanted to the site by autogenous bone, bone marrow aspirate and/or cell implantation.
As no ‘ideal’ bone graft currently exists, autograft bone, often recovered from patients' iliac crest, is considered the “gold standard.” However, autograft bone involves additional surgical trauma to the patient, time/cost of additional surgical time and supplies, and often results in patient morbidity that may be slow to resolve. Quantities of autograft bone are also limited, and this becomes more problematic in patients with prior bone harvesting procedures. Furthermore, the healing rates, particularly recognized in animal models designed to study bone graft performance, (e.g., rabbit posterolateral spine fusion) have demonstrated less than optimal results, i.e., 70% spine fusion rates. Considering the requirements to form bone, a need exists for a reproducible and cost-effective process of making a bone graft having improved osteoconductive and osteoinductive properties.